STEERING 2 GENERAL DESCRIPTION The EPAS (Electrical Power Assisted Steering - column mounted) is made up of the following components The system consists of the steering column and a servo unit. The steering torque is transmitted via the intermediate shaft with universal joints to the mechanical rack and pinion steering. Sensor technology and torsion bar are next to the helical gear drive in the servo unit. The helical gear drive converts the support torque generated by the servo motor and transmits it to the intermediate shaft. The support torque and operating torque of the steering wheel generated are transmitted via the intermediate shaft to the mechanical rack-andpinion steering gear and then to the front wheels. If the vehicle power supply or electrical supply fails, then the vehicle can still be steered due to the mechanical connection between the steering wheel and front tires being steered. EPAS system is equipped with following assist feature 1. Speed Sensitive Assist Control 2. Active Return Control FUNCTION The torque sensor in servo unit registers the steering torque and steering speed once the driver performs a steering motion. All data (including the vehicle signals such as engine speed, vehicle speed, ignition signal) is transmitted to the control unit (ECU). This then calculates the necessary support torque and on the basis of the calculated results, controls the servo motor. A rotor position sensor is attached to the servo motor. An index sensor is integrated in the torque sensor. The control unit uses the integrated index sensor and the rotor position sensor to calculate the steering wheel’s steering angle. Depending on the programming, the steering wheel’s angle signal can be sent back to the vehicle. 3. BLOCK DIAGRAM OF EPAS SYSTEM:
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